Currently, methods for vital staining of human epithelial tumor cells primarily include methods based on acetowhite test, iodine test, toluidine blue test, methylene blue staining, hematoxylin staining and the like.
Specifically, the acetowhite test is to smear acetic acid solution, for example, 3˜5% acetic acid solution, on the cervical/vaginal epithelial tissue, and observe whether there is any acetowhite responsive region in the smeared epithelial tissue after waiting for some time. If there is any acetowhite region, this epithelial tissue is suspected to contain tumor cells. However, although this method has high sensitivity, its specificity is poor, that is because besides tumor cells, some inflammatory cells can also generate acetowhiteness, thereby producing false positive results. Moreover, the specificity of this method is heavily affected by the operator's skill level and experience.
The mechanism of the iodine test is reaction with glycogen. It involves smearing Lugol's iodine on cervical epithelial tissues and detecting by observing the iodine staining of the epithelial cells, in which normal epithelium exhibits red-brown or black, whereas abnormal epithelium exhibits thick mustard yellow or yellowish brown. However, if there is epithelial inflammation, these regions may not be stained by iodine, or exhibit colorless loading. Therefore, iodine test has poor specificity on the staining of the epithelial cells[1].
Methods using toluidine blue may cause the staining of the nuclear debris of neutrophils and bacterial, resulting in high false positive rate. It is also difficult to stain cancer and leukoplakia with surface keratinization, which tends to cause false negative[2].
After staining of epithelial tissues with hematoxylin, a high power microscope is needed for observation with complicated operation and high requirements on the expertise and experience of the operator, as well as long inspection time.
The affinity between methylene blue and cancer cells makes malignant tissues prone to blue staining. It is reported that using it for in situ biopsy sampling of esophageal epithelial tissues has the effect of improving positive rate of biopsy[3]. However, there is no report in the art to combine the redox color change reaction of methylene blue with folic acid or folic acid complex so as to rapidly locate and detect epithelial tumor cells by staining and color change reaction.
A composition for detecting epithelial tumor cells, especially, for cervical/vaginal epithelial tissue tumor cells by staining and color change which has high sensitivity, high specificity and simple and rapid operation is urgently needed in the art.